It is known in the art relating to high speed rotor applications, such as in gas turbine engines, turbochargers and the like that dynamic unbalance generates vibrations during rotor rotation which may be controlled or damped by squeeze film type dampers. Examples of such dampers in combination with anti-friction type bearings are described in U.S. Pat. No. 4,527,912 Klusman issued Jul. 9, 1985 to the assignee of the present invention.
In the art relating to relatively heavy duty diesel engines, particularly two cycle diesel engines of the type produced by the Electro-Motive Division of General Motors Corporation and used extensively in diesel-electric railway locomotives and numerous other applications, the use of overrunning gear driven turbochargers is also known. Some such embodiments are described and/or referred to in U.S. Pat. No. 4,719,818 McCreary issued Jan. 19, 1988 to the assignee of the present invention. In an embodiment described in this patent, the turbocharger rotor 14 is supported on lobed sleeve bearings, not numbered, including a compressor bearing supporting a journal between the turbine wheel 15 and an overhung compressor wheel 16. Such compressor bearings have included a sleeve having five tapered (offset cylindrical) internal lobes and an integral spherical thrust flange, the sleeve being fixed in the turbocharger housing. Pressure oil is supplied to the bearing through feed grooves at the deeper edges of wedge shaped oil spaces formed by the lobes.
The five tapered lobe sleeve bearing with integral thrust flange has given many hours of satisfactory service in turbochargers of the type described in U.S. Pat. No. 4,719,818. However, it has been found through extensive testing that the dynamics of the turbocharger rotor with its overhung compressor limit bearing life in operation under some operating conditions involving synchronous critical speeds, resonances and subsynchronous instabilities such as "oil whirl" and "oil whip".